Work holding fixture

ABSTRACT

A hydraulic work-holding fixture is arranged and constructed such that initial arcuate movement of an operating lever is effective to swing a work-engaging plunger into a predetermined plane for alignment with a workpiece, while further arcuate movement is effective to hydraulically extend the plunger for engagement with the workpiece, the plunger is automatically retracted unless the device is fully actuated; an elastically deformable member exposed to fluid within the device provides variation in the extension of the plunger in order to accommodate tolerances in the workpiece.

United States Patent Inventor Otis L. Butler Decatur, Ill. Appl. No. 867,616 Filed Oct. 20, 1969 Patented Aug. 10, 1971 Assignee Borg-WarnerCorporation Chicago, Ill.

WORK HOLDING FIXTURE 5 Claims, 2 Drawing Figs.

US. Cl 269/23, 60/545, 269/25, 269/29 lnt. B23q 3/08 Field of Search 269/20, 23. 25. 27, 28, 29, 32, 31 60/545, 92/60 References Cited UNITED STATES PATENTS 2,310,519 2/1943 Eskin 73/3683 2/1948 Marsilius 269/32 X 2,402,411 6/1946 Kent,v 269/28 2,977,764 4/1961 Matthews 92/60 X FOREIGN PATENTS 591,756 1947 Great Britain 269/29 Primary Examiner-Andrew R. .Iuhasz Assistant Examiner-Donald D. Evenson Attorneys-Donald W Banner, William Sv McCurry and John W. Butcher ABSTRACT: A hydraulic work-holding fixture is arranged and constructed such that initial arcuate movement of an operating lever IS efiective to swinga work-engaging plunger into a predetermined plane for alignment with a workpiece, while further arcuate movement is effective to hydraulically extend the plunger for engagement with the workpiece, the

plunger is automatically retracted unless the device is fully ac-' tuated; an'elastically deformable member exposed to fluid within the device provides variation in the extension of the plunger in order to accommodate tolerances in the workpiece PATENTEU AUBIOIBYI 3,598,391

FIGZ

INVENTOR. 67 OTIS L. BUTLER BY $7 M 5M ATTORNEY WORK HOLDING FIXTURE SUMMARY OF THE INVENTION The present invention relates generally to work-holding fixtur'es and more particularly to improved hydraulically powered fixtures.

A work-holding fixture for clamping articles during machindimensional variations in the article. It is, an object of the present invention to provide an improved work-holding-fixturcincorporating these and other desirable features.

One advantage ofthc work-holding fixture according to the present invention is the provision of a clamping device in' which movement of an operating handle in onedirection is effective to first release the clamping force and then to swing the clamp out of the way allowing ample room for removal of a finished workpiece and set up of another unfinished workpiece. Movement of the operating handle in the other direction is effective to first swing the clamping'member into position and then to extend the clamping member into engagement with the workpiece.

Another advantage of the present structure resides in the provision of manual lever and cam-operating means in com-.

Central body portion 29 includes an external abutment 39 engageable with abutment 26 for limiting the arcuate movement of fixture I about the axis through trunnion members v 21, 22. An external projection M on central body portion 29 is received within bearing surface 28 pivotally supporting body I2 in base 11. Cap portion 31 is provided with a similar external projection 42 received within bearing surface 27 of base II. A sleeve 43 formed of bearing material may be inserted in bore 34, if desired, providing a stepped bore 46 concentric with first cylindrical bore 44.

An operating piston 47 is received within chamber 33 and includes a neck portion 48 arrangedfor longitudinal move- ,me'nt' along bore 44. Neck portion 48 includes a pair of bination with hydraulic pistons affordinga measure of force multiplication for securely clamping a workpiece. The cam and lever means includes camming surface and dwell surface for distinguishing between full and partial clamping engagement, thus reducing operator error which might result in subsequent dislodgment of the workpiece. v

A further advantage of the device resides in the provision of means for retracting the clamping member from the workpiece unless the device is fully actuated.

A still further advantage'resides in the provision of a rubberlike block exposed to the working fluid which permits variable extension of the'clamping member in order to accommodate dimensional tolerance in the workpiece while avoiding tedious and time consuming adjustments to the clamping member.

These and other objects and advantages of the present in vention will become more fully apparent from consideration of the following description together with the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I isan elevation view of a work-holding fixture according to the present invention, and

FIG. 2 is a sectionview taken along FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in more detail to FIGS. I and 2, the fluidactuated work-holding fixture I0 includes a base portion II, a body member 12, a work-engaging plunger I3, and an actuating lever 14 to be described in more detail hereinafter.

Base portion 11 includes a pair of'generally' similar supporting members 16, I7, each having a foot portion I8, I9 and an associated trunnion like sidewall portions 21, 22. Foot portions I8, I9 are provided: with apertures for receiving cap screws 23, providing means for securing the fixture I0 to the bed plate 24 of a machine tool. Supporting nicmhcr I6 is also provided with an abutment 26 arrangcd to limit the arcuate movement of body member I2. Sidcwall portions 2i, 22 inelude bearing surfaces 27, 28, supporting body I2 for rota= tional movement with respect to base I I.

Body member l2'includcs a central portion 29, an axial cap portion 3|, and a radial cap portion 32' secured together in unitary assembly, defining therein a fluid chamber 33, a first cylindrical bore 44 extending along an axis through trunnion members 21, 22, a second bore 36 extending transversely with respect to first bore 44', and fluid passages 37, 38 communicating chamber 33 with second bore 36.

the section line 2-2 of keyways 49, 51 engaged with pins 52, 53 preventing rotational movement of piston 47 with respect to body I2. An end of neck portion 48 is provided with camming means including inclined surface 54 anddwell surface 56. Operating piston 47 also includes a fluid engaging face 57 and a receptacle 58 spaced from the neck portion. An elastically deformable block 59 formed of an elastomeric material is received within receptacle 58 and exposed to fluid within chamber 33. A seal ring 68 is disposed about piston 47 providing a fluidtight seal between the external surface of the piston and the walls of fluid chamber 33.

Actuating lever I4 is secured to a drive member 61 received within sleeve 43. Drive member 61 includes a head portion 62 disposed within bore 44 and having a drive surface 63, 64 engageable with the camming surfaces 54, 56 of piston 47. A shank portion extends through stepped bore 46 and terminates in a hexagonally flatted external end portion 67 providing a drive connection with lever I4.

Work-engaging plunger 13 includes a piston 69 received within second bore 36 having a face portion 71 exposed to fluid contained within chamber 33 and passages 37, 38. A ring seal 72 provides a fluidtight seal between piston portion 69 and bore 36. A shank portion 73 extends outwardly from piston portion 69 through radial cap portion 32 terminating in a threaded portion 74. Arcturn spring 76 is disposed between piston portion 69 and cap 32 urging plungcr I3 to a retracted position as shown in solid lines in FIGS. l and 2. A work-engaging clamp member 77 is udjustably secured to threaded portion 74 of plungcr I3. Lock nut 78 is provided for retaining clamp'rncmber 77 in a predetermined positionwith respect to the other portions of plunger I3.

OPERATION The advantages of the present work-holding fixture can be more fully appreciated in terms of an operating sequence. Initially, .the fixture I0 is positioned such that operating lever I4 is in a horizontal position as indicated by 14' in FIG. I. In this initial position, the body I2 is pivoted in trunnions 2I. 22 such that radial cap portion 32 extends vertically upwardly from base It as indicated by 32 in FIG. I. In the initial position, ample space is provided adjacent base II for setting up a workpiece indicated by the broken lines 81, 82 in FIG. I.

In order to actuate the fixture for clamping engagement with the workpiece, the operator moves lever I4 in a clockwise direction as indicated by the arrow 83 from the position l4 to the position I4". Initial pivotal movement of lever I4 is effective to rotate body I2 in trunnions 2I, 22 until ahutmcnts 39, 26 engage each other. As indicated by arrow 64', plungcr I3 is thus moved into a horizontal plane into align ment with workpieces ill, tl2. Further pivotal movement of lever I4 to the position I4" is effective to extend plungcr I3 into engagement with workpieces 8t. 82 as indicated by the arrow 86. I

Referring to FIG. 2, initial pivotal movement of lever I4 exerts a turning force on drive member 61 which is transmitted to piston 47 by means of the drive surface 63 and inclined cam surface 54. Piston 47 is keyed to body 12 by means of the keyways 49, SI and pins 52, 53 such that body I2 is required to turn with piston 47 until the abutments 26, 39 engage each other. Further arcuate movement of lever 14 results in relative movement between the drive surface 63 and inclined cam surface 54 thus driving piston 47 inwardly in a direction to displace fluid from chamber 33. The displacement of piston 47 is fixed as determined by the drive surface 64 and dwell surface 56. Displacement of piston 47 results in extension of plunger 13 as determined by the movement of fluid from chamber 33 through passages 37, 38 into bore 36. The inclination of drive surface 63 and cam surface 54 is such that if the operator fails to move the lever far enough to engage drive surface 64 with dwell surface 56, the lever will return to the vertical position and the plunger will retract from the workpiece under the urgence of return spring 76. On the other hand, when the operator moves the lever through sufficient arc, to fully actuate the device, the surfaces 64 and 56 engage each other, holding piston 47in displaced position such that the plunger extends into engagement with the workpiece and remains in its extended position. This provides an extremely reliable indication to the operator, as to whether the plunger is properly engaged with the workpiece, thus avoiding subsequent dislodgment of the workpiece due to partial engagement.

The fixture is disengaged from the workpiece in substantially reverse order. For example, counterclockwise movement of lever l4 from the position indicated by 14'', is effective to slide the surfaces 56, 64 out of engagement with each other. Return spring 76 then becomes effective to retract plunger 13 from the workpiece resulting in inward movement of piston 69 and corresponding outward movement of piston 47. Outward movement of piston 47 assures continued en gagement of neck portion 48 with the head 62 of the drive member 61. Surface 87 of drive member head 62 then engages surface 88 of piston neck 48, resulting in rotation of piston 47 and body 12 to the upright position indicated by 32'. The finished workpiece can then be removed and another workpiece set up onbed plate 24, after which the fixture is reactuatcd as previously described.

As indicated by broken lines 81, 82, the workpieces with which the device is used may be expected to have a dimensional tolerance requiring that the nose member 77 undergo a variation in extensile movement in order to exert an effective clamping force. The elastomeric block 59 is exposed to fluid pressure in chamber 33 and is adapted to undergo distortion within receptacle 58 thus modifying the effective volume of chamber 33. Thus a substantially incompressible fluid may be employed in the fixture in combination with a drive piston having a fixed displacement, and yet result in a range of displacements of plunger 13 sufficient to accommodate tolerances in the workpiece. For example, where the ratio of the areas of pistons 47 and 69 is 4 to 1, an axial displacement of piston 47 in the amount of 0. l 25 inch provides an extension of plunger 13 in the range of from 0.468 to 0.53] inches thus accommodating a tolerance in the workpiece of 0.062 inches while maintaining an effective clamping force.

The foregoing description is directed to a preferred embodiment of the device as shown in the drawing, however, various modifications thereof are comprehended within the spirit and scope of the invention.

Whatl claim is:

l. A fluid actuated work-holding fixture including a body member defining a fluid chamber therein;

an operating piston connected to said body member for communication with said fluid chamber, said piston being ments in accordance with the effective volume of said chamber; and

an elastically deformable block member having a fluid-engaging face portion communicating with said chamber said b ock member being deformab e in response to flui pressure in said chamber for varying the effective volume thereof.

2. A fluid actuated work-holding fixture according to claim 1, including camming means engageable with said operating piston effective for moving said piston through said predetermined displacement, said body member including return spring means engaged with said plunger effective for retracting said plunger in response to partial displacement of said piston.

3. A fluid actuated work-holding fixture according to claim 1, said operating piston defining a receptacle portion, said block member being formed of an elastomeric material and received within said receptacle portion.

4. A fluid actuated work-holding fixture according to claim I, said body member including a substantially cylindrical bore portion adjacent said fluid chamber, said operating piston being of substantially cylindrical form and received within said bore portion for longitudinal movement with respect to said chamber, said operating piston including a cam surface disposed remotely from said chamber, said cam surface including an inclined portion and a dwell portion, and actuating means engaged with said'cam surface effective to move said piston longitudinally of said bore portion, said dwell portion of said cam surface limiting the displacement of said piston.

5 A fluid actuated work-holding fixture according to claim I, said fixture including a base member supporting said body member for limited rotational movement about an axis, said body member including a substantially cylindrical first bore portion extending along said axis adjacent said fluid chamber, and a second bore portion extending transversely of said axis communicating with said fluid chamber, said second bore portion receiving said work-engaging plunger for extensible movement with respect to said body member; said operating piston being of substantially cylindrical form received within said first bore, said piston having a slidable keyway connection with said body member permitting longitudinal movement along said axis and prohibiting rotational movement with respect to said bore portion, said piston having a cam surface remote from said chamber including an inclined portion and a dwell portion, and an actuating lever mounted on said body member for pivotal movement about said axis, said lever in cluding a driving surface engageable with said cam surface, said actuating lever being effective to rotate said body member with respect to said base member in response to initial pivotal movement thereof for positioning said plunger with respect to said base, and to drive said piston through a predetermined displacement in response to further pivotal movement thereof for extending said plunger with respect to said body member. 

1. A fluid actuated work-holding fixture including a body member defining a fluid chamber therein; an operating piston connected to said body member for communication with said fluid chamber, said piston being mounted for movement through a predetermined displacement for exerting fluid pressure in said chamber; an extensible work-engaging plunger having a fluid-engaging face portion communicating with said fluid chamber, said workengaging plunger being mounted for extension with respect to said body member, in response to fluid pressure in said chamber, through a range of displacements in accordance with the effective volume of said chamber; and an elastically deformable block member having a fluid-engaging face portion communicating with said chamber, said block member being deformable in response to fluid pressure in said chamber for varying the effective volume thereof.
 2. A fluid actuated work-holding fixture according to claim 1, including camming means engageable with said operating piston effective for moving said piston through said predetermined displacement, said body member including return spring means engaged with said plunger effective for retracting said plunger in response to partial displacement of said piston.
 3. A fluid actuated work-holding fixture according to claim 1, said operating piston defining a receptacle portion, said block member being formed of an elastomeric material and received within said receptacle portion.
 4. A fluid actuated work-holding fixture according to claim 1, said body member including a substantially cylindrical bore portion adjacent said fluid chamber, said operating piston being of substantially cylindrical form and received within said bore portion for longitudinal movement with respect to said chamber, said operating piston including a cam surface disposed remotely from said chamber, said cam surface including an inclined portion and a dwell portion, and actuating means engaged with said cam surface effective to move said piston longitudinally of said bore portion, said dwell portion of said cam surface limiting the displacement of said piston.
 5. A fluid actuated work-holding fixture according to claim 1, said fixture including a base member supporting said body member for limited rotational movement about an axis, said body member including a substantially cylindrical first bore portion extending along said axis adjacent said fluid chamber, and a second bore portion extending transversely of said axis communicating with said fluid chamber, said second bore portion receiving said work-engaging plunger for extensible movement with respect to said body member; said operating piston being of substantially cylindrical form received within said first bore, said piston having a slidable keyway connection with said body member permitting longitudinal movement along said axis and prohibiting rotational movement with respect to said bore portion, said piston having a cam surface remote from said chamber including an inclined portion and a dwell portion, and an actuating lever mounted on said body member for pivotal movement about said axis, said lever including a driving surface engageable with said cam surface, said actuating lever being effective to rotate said body member with respect to said base member in response to initial pivotal movement thereof for positioning said plunger with respect to said base, and to drive said piston through a predetermined displacement in response to further pivotal movement thereof for extending said plunger with respect to said body member. 